138 



GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



by strong faults that strike north and dip east. Strangely enough these faults 

 have not been recognized on the surface, at the points where they should 

 outcrop, but of their importance underground there is no doubt. 



The slip and cut-off at the west end of the Silver Top workings must be only 

 about 70 feet perpendicularly distant from the slip which cuts off the Valley View 

 vein on the east, on the 200-foot level. The two can be treated together, then, as 

 a fault zone, in which the main slip may or may not have been cut, but must either 

 be one of those cut or must lie in the narrow zone between them. Moreover, 

 the flat-dipping Valley View vein, which is thus cut off on the 200-foot level. 



Valley View shaft 



Store Cabin shaft 

 8OI 



ZOO-ft. level, 7 feet below 

 Valley View ZOOft.level 



50 



200 feet 



FIG. 33. Horizontal plan of veins in Valley View and Stone Cabin workings on the plane of the Mizpah 200-foot level, 

 to show the probable connection between the chief veins on the two sides of the Valley View fault. 



would, if continued, almost exactly strike, at this level, the nearly vertical main 

 Silver Top ledge, which trends in the same direction (fig. 33). 



Hypotheses to explain fault movement. The suggestion arises that the Silver 

 Top and the Valley View may be really parts of the same vein, and that faulting 

 is responsible for the remarkable differences in dip on the two sides of the 

 fault. Both are plainly the downward extension of the strongest portion of the 

 same outcropping vein system. We may at first consider the hypothesis whether 

 the fault has had a twisting movement so as to tilt the vein on one side more 

 than on the other. This difference in tilt, however, would be about 45, and 

 would involve such an extraordinary rotation of the rocks on one side of the 



